I don't know why you asked this but of course there are many options. Perhaps, they migrated over from gmail after the 2010 hacking of Chinese human rights activists accounts.

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Originally Posted by BigRedChief

Why would you use something so easily hacked? No underground taking it to the man would use Twitter for private conversations. That ship sailed years ago.

Since when is Twitter easily hacked? This is the first time they've had their data breached and they caught it in the act and stopped it. Most companies don't know until months or years later. I think of twitter as having a strong reputation in terms of security and protecting privacy of user data.

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Twitter’s efforts to recruit two of the security community’s most high profile hackers may seem a bit puzzling. But Twitter has been taking pains to prove to users that it aims to protect their privacy and, in some cases, anonymity, to a degree that trumps Facebook and even Google. It remains one of the only mainstream social media services that allows the use of pseudonyms. And it’s currently fighting a landmark legal battle to avoid having to turn over the tweets of Malcolm Harris, an Occupy Wall Street protestor who was charged with disorderly conduct last year.

All of those moves seem designed to define Twitter as a place where users–especially political vulnerable ones–can let loose with controversial political speech without worrying about being identified by government requests or kicked off the service. With the addition of security stars like Miller and Marlinspike, it seems Twitter is aiming to make sure those users are protected from less benevolent hackers, too.